The present invention relates to seating, and in particular to an integrated chair and control arrangement therefor.
Articulated seating, such as tilt back chairs, and other furniture articles of the type having at least two, mutually adjustable portions, are used extensively in office environments. The mutually adjustable portions of the seating are normally interconnected by a controller or control, which mechanically adjusts the mutual orientation of the various adjustable seating portions. Seating controls normally include springs which bias the seating into a normal or upright position. The controls also typically include some type of adjustment device to vary the biasing force which resists movement of the adjustable portions of the seating from their normal position.
Synchrotilt chair controls, such as the device disclosed in U.S. Pat. No. 4,390,206 to Faiks et al., and assigned to the assignee of the present application, provide a mechanism which causes the chair back to rotate at a rate different from that of the chair bottom or seat. Such mechanisms are generally referred to as "synchrotilt" controls, since the chair back and chair bottom move in a synchronous fashion. Normally, synchrotilt controls cause the chair back to tilt at a faster rate than the chair bottom, so that as the user tilts the chair back rearwardly, the user's feet are less likely to be lifted off of the floor by the rising front edge of the chair bottom.
Chair controls are normally mounted below the chair bottom, so that they do not interfere with the use of the chair, and so that they do not detract from the aesthetics of the chair design. As a result, the axis about which the chair back and chair bottom rotate with respect to each other, which is referred to herein as the "common axis" or the "synchrotilt axis," is also disposed below the chair bottom. In such chairs, the common axis and/or the synchrotilt axis of the chair is not located adjacent to, or anywhere near the hip joints of the seated user, which is where the user's upper body or torso pivots naturally and comfortably with respect to the user's legs. The hip joints of an average user, seated upright with good posture in the chair, normally lie along an imaginary, generally horizontally oriented axis above the seating surface of the chair bottom, approximately 3 to 4 inches, and forwardly of the plane of the seating surface on the chair back, approximately 3 to 5 inches. The position of this "hip joint axis" in side elevational view with respect to a chair is generally referred to as the "H" point. Although the "H" point varies from one individual to another, depending upon the particular size, shape and other physical characteristics of the user, a model or preferred "H" point can be derived empirically, based upon studies of a wide range of different types of users.
Prior synchrotilt chair controls, such as that disclosed in the previously noted Faiks et al. U.S. Pat. No. 4,390,206, have a rather complicated construction, and are rather large and bulky. Such devices have a two-part articulated iron construction, with a fixed axle about which back and seat support portions of the iron rotate. The control is completely separate or independent from the chair or shell, and mutually rotates the chair back and chair bottom about the fixed axle, which is located below the chair bottom.
When the common or synchrotilt axis of the chair is spaced a significant distance front the "H" point, for example in the nature of 5 to 8 inches, the chair does not flex or articulate in a comfortable, natural fashion in tune with the user's body. When the synchrotilt axis is located below the chair bottom or seat, the chair back tends to pull away from the lumbar area of the user as the chair back tilts rearwardly. As a result, the user's lumbar area does not receive full support throughout all chair positions, and some degree of muscle fatigue can possibly result.
Also, when the common or synchrotilt axis of a chair is not located adjacent to the "H" point, as the chair back tilts rearwardly, the chair back moves longitudinally along the user's back, and rubs or abrades on the same. This motion can be somewhat uncomfortable, but more importantly, typically dishevels or otherwise pulls the user's clothing from their proper position. For example, if the user is wearing separate top and bottom clothes, such as a shirt and pants, rearward tilting of the chair back will pull the user's shirt from its proper position in the user's pants.
Hence, it is apparent that in seating design it is beneficial, for a number of different reasons, to locate the rotational axis of the chair back and chair bottom as close to the "H" point as possible.